The invention relates to piezo-electric acoustic transducers for electro-acoustic capsules with two terminal elements in the form of strip-shaped terminal leads or wires for the transducer. One of the leads is contacted to an adhesive-side electrode of piezo-ceramic, and the second lead is soldered onto the other electrode. The invention further relates to devices for soldering the terminal leads onto the conductor paths of a flat amplifier assembly and for mounting this flat assembly on the carrier plate.
Piezo-electric acoustic transducers are installed in telephone devices, preferably in mouth-pieces (microphones), ear-pieces, and ringing capsules. With the exception of an ear-piece type, the transducer always has two terminal strips: one strip is contacted through to the adhesive-side electrode of the piezo-ceramic (see German OS No. 28 20 403, corresponding to British Patent No. 2,020,921, incorporated herein by reference) and the second of which is soldered to the other electrode.
Previously the two terminal leads of the transducer plate have been manually soldered to Griplet soldering rivets on the components side of the circuit board with the addition of soldering tin. For this purpose the separating plate, the silicon rings, the transducer plate, the carrier and the amplifier assembly must be pre-assembled. The application of a synthetic ring prevents an electric short-circuit occurring between the metal housing and the terminal leads. This assembly and soldering procedure is expensive, fault prone, and cannot be automated.
FIG. 1 illustrates the previous construction of a mouth-piece. Reference numeral 1 designates the housing under the surface of which there is arranged a damping ring 2. Beneath the damping ring is arranged a separating plate 3 as a structural support element. The transducer is formed of a transducer plate 4 comprising electrically conductive material, and of a disc of piezo-ceramic which is provided with electrodes on both its sides and over its entire surface. The piezo-ceramic, which is provided with the electrodes, is permanently connected to the transducer plate 4 by adhesive. The transducer plate 4 is supported by two silicon rings 5a and 5b. The through-contacted terminal lead or strip is not represented in the illustrated sectional plane. The soldered-on terminal lead 6 is guided between the transducer plate 4 and silicon ring 5, and between a synthetic carrier 7 and the metal housing 1 to the component side of an amplifier assembly 9 where it is soldered to Griplet soldering rivets 8. Reference numeral 10 designates a synthetic ring which protects the two terminal leads or strips from the metal housing of the piezo-microphone so as to prevent a short-circuit. An insulating body 11 is arranged in the lower region of the housing.